1. Field of the Invention
The present invention relates to an external combustion engine converting the displacement of a liquid part of a working medium occurring due to generation of vapor of the working medium and a change in volume of the working medium accompanying liquefaction to mechanical energy for output.
2. Description of the Related Art
In the past, as one external combustion engine, an engine configured formed with a heater for heating part of a working medium in a container in which the working medium is sealed flowable in the liquid state so as to generate vapor of the working medium and a cooler for cooling the vapor of the working medium to liquefy it, to change the volume of the working medium along with this generation and liquefaction of the vapor of the working medium, and to take out the displacement of the liquid part of the working medium occurring due to the change in volume of the working medium as mechanical energy is disclosed in Japanese Patent Publication (A) No. 2005-330885.
In this related art, the portion connecting the heater and cooler in the container is split into a plurality of tubular parts so as to form in effect a plurality of heaters and coolers corresponding to the plurality of tubular parts and thereby increase the heat transfer areas of the heater and cooler. Due to this, the working medium is improved in heating performance and cooling performance and the output of the external combustion engine is improved.
Here, if forming a plurality of heaters corresponding to the plurality of tubular parts, the timing of generation of vapor of the working medium (timing of rise in pressure) will end up differing for each tubular part. For this reason, the internal pressure of the slow vapor generation timing tubular parts will become higher than the internal pressure of the fast vapor generation timing tubular parts and a pressure difference will occur between the plurality of tubular parts.
For this reason, if the vapor of the working medium increases in volume and the liquid part of the working medium displaces, part of the liquid part of the working medium will end up displacing from the slow vapor generation timing tubular part to the fast vapor generation timing tubular part side and will not displace toward the output part. As a result, the problem arises that part of the displacement of the liquid part of the working medium cannot be effectively taken out as mechanical energy and the efficiency of the external combustion engine ends up falling.
As a measure to deal with this problem, in the related art, the plurality of heaters are connected with each other. Due to this, even if the timing of generation of vapor of the working medium differs between the plurality of tubular parts, the internal pressures of the plurality of tubular parts can be made the same pressure, so a difference in internal pressures between the plurality of tubular parts can be avoided.
For this reason, it is possible to prevent part of the liquid part of the working medium from ending up displacing from the slow vapor generation timing tubular part side to the fast vapor generation timing tubular part side, so a drop in the efficiency of the external combustion engine can be suppressed.
However, according to detailed studies of the present inventors, it was learned that there is room for further improvement of the output of the external combustion engine of this related art in the following point. That is, in this related art, since a plurality of heaters are connected, the vapor of the working medium moves from the slow vapor generation timing tubular parts to the fast vapor generation timing tubular parts.
This being the case, the vapor of the working medium moving to the fast vapor generation timing tubular parts ends up becoming mixed with the liquid part of the working medium in the fast vapor generation timing tubular parts and forming bubbles. If the vapor of the working medium mixes with the liquid part of the working medium and forms bubbles in this way, it is learned that the vapor of the working medium ends up being cooled by the liquid part of the working medium and liquefies, so the amount of displacement of the liquid part of the working medium ends up being reduced by that amount and the output of the external combustion engine ends up falling.